The present invention relates to the field of corn breeding. In particular, the present invention relates to an inbred corn plant designated MBZA and derivatives of that inbred plant.
The goal of field crop breeding is to combine various desirable traits in a single variety/hybrid. Such desirable traits include greater yield, better stalks, better roots, resistance to insecticides, pests, and disease, tolerance to heat and drought, reduced time to crop maturity, better agronomic quality, and uniformity in germination times, stand establishment, growth rate, maturity, and fruit size.
Breeding techniques take advantage of a plant""s method of pollination. There are two general methods of pollination: a plant self-pollinates if pollen from one flower is transferred to the same or another flower of the same plant. A plant cross-pollinates if pollen comes to it from a flower on a different plant.
Corn plants (Zea mays L.) can be bred by both self-pollination and cross-pollination. Both types of pollination involve the corn plant""s flowers. Corn has separate male and female flowers on the same plant, located on the tassel and the ear, respectively. Natural pollination occurs in corn when wind blows pollen from the tassels to the silks that protrude from the tops of the ears.
Plants that have been self-pollinated and selected for type over many generations become homozygous at almost all gene loci and produce a uniform population of true breeding progeny, a homozygous plant. A cross between two such homozygous plants produce a uniform population of hybrid plants that are heterozygous for many gene loci. Conversely, a cross of two plants each heterozygous at a number of gene loci produces a population of hybrid plants that differ genetically and are not uniform.
The development of uniform corn plant hybrids requires the development of homozygous inbred plants, the crossing of these inbred plants, and the evaluation of the crosses. Pedigree breeding and recurrent selection breeding methods are used to develop inbred plants from breeding populations. Those breeding methods combine the genetic backgrounds from two or more inbred plants or various other broad-based sources into breeding pools from which new inbred plants are developed by selfing and selection of desired phenotypes. The new inbreds are crossed with other inbred plants and the hybrids from these crosses are evaluated to determine which of those have commercial potential.
The pedigree breeding method for single-gene traits involves crossing two genotypes. Each genotype can have one or more desirable characteristics lacking in the other; or, each genotype can complement the other. If the two original parental genotypes do not provide all of the desired characteristics, other genotypes can be included in the breeding population. Superior plants that are the products of these crosses are selfed and selected in successive generations. Each succeeding generation becomes more homogeneous as a result of self-pollination and selection. Typically, this method of breeding involves five or more generations of selfing and selection: S1xe2x86x92S2; S2xe2x86x92S3; S3xe2x86x92S4; S4xe2x86x92S5, etc. After at least five generations, the inbred plant is considered genetically pure.
Backcrossing can also be used to improve an inbred plant. Backcrossing transfers a specific desirable trait from one inbred or source to an inbred that lacks that trait. This can be accomplished for example by first crossing a superior inbred (A) (recurrent parent) to a donor inbred (non-recurrent parent), which carries the appropriate gene(s) for the trait in question. The progeny of this cross are then mated back to the superior recurrent parent (A) followed by selection in the resultant progeny for the desired trait to be transferred from the non-recurrent parent. After five or more backcross generations with selection for the desired trait, the progeny are heterozygous for loci controlling the characteristic being transferred, but are like the superior parent for most or almost all other genes. The last backcross generation would be selfed to give pure breeding progeny for the gene(s) being transferred.
A single cross hybrid corn variety is the cross of two inbred plants, each of which has a genotype which complements the genotype of the other. The hybrid progeny of the first generation is designated F1. Preferred F1 hybrids are more vigorous than their inbred parents. This hybrid vigor, or heterosis, is manifested in many polygenic traits, including markedly improved higher yields, better stalks, better roots, better uniformity and better insect and disease resistance. In the development of hybrids only the F1 hybrid plants are sought. An F1 single cross hybrid is produced when two inbred plants are crossed. A double cross hybrid is produced from four inbred plants crossed in pairs (Axc3x97B and Cxc3x97D) and then the two F1 hybrids are crossed again (Axc3x97B)xc3x97(Cxc3x97D).
The development of a hybrid corn variety involves three steps: (1) the selection of plants from various germplasm pools; (2) the selfing of the selected plants for several generations to produce a series of inbred plants, which, although different from each other, each breed true and are highly uniform; and (3) crossing the selected inbred plants with unrelated inbred plants to produce the hybrid progeny (F1). During the inbreeding process in corn, the vigor of the plants decreases. Vigor is restored when two unrelated inbred plants are crossed to produce the hybrid progeny (F1). An important consequence of the homozygosity and homogeneity of the inbred plants is that the hybrid between any two inbreds is always the same. Once the inbreds that give a superior hybrid have been identified, hybrid seed can be reproduced indefinitely as long as the homogeneity of the inbred parents is maintained. Conversely, much of the hybrid vigor exhibited by F1 hybrids is lost in the next generation (F2). Consequently, seed from hybrid varieties is not used for planting stock. It is not generally beneficial for farmers to save seed of F1 hybrids. Rather, farmers purchase F1 hybrid seed for planting every year.
North American farmers plant over 70 million acres of corn at the present time and there are extensive national and international commercial corn breeding programs. A continuing goal of these corn breeding programs is to develop high-yielding corn hybrids that are based on stable inbred plants that maximize the amount of grain produced and minimize susceptibility to environmental stresses. To accomplish this goal, the corn breeder must select and develop superior inbred parental plants for producing hybrids.
In one aspect, the present invention provides a corn plant designated MBZA. The present invention also provides seed of corn plant MBZA, which seed has ATCC Accession No. PTA-3879, and a corn plant having the functional and morphological characteristics of corn plant MBZA.
In another aspect, the present invention provides a tissue culture of corn plant MBZA. Preferably, a tissue culture comprises embryos, protoplast, meristematic cells or pollen. Still further, the present invention provides a corn plant regenerated from a tissue culture of this invention.
In yet another aspect, the present invention provides a process of preparing a corn plant comprising crossing a first parent corn plant with a second parent corn plant wherein at least one of the parent corn plants is inbred corn plant MBZA. In a preferred embodiment, crossing comprises planting in pollinating proximity seeds of the first and second parent corn plant; growing the seeds of said first and second parent corn plant into plants that bear flowers; emasculating the flowers of the first or second parent corn plant to produce an emasculated parent corn plant; allowing cross-pollination to occur between the first and second parent corn plant; and harvesting the seeds from the emasculated parent corn plant.
In one embodiment, the process comprises crossing a female corn plant with a male corn plant where either the female corn plant or the male corn plant is corn plant MBZA.
The present invention also contemplates a corn plant produced by a process comprising crossing a first parent corn plant with a second parent corn plant wherein at least one of the first and second parent corn plants is corn plant MBZA. In one embodiment, a corn plant produced by the process is an F1 hybrid corn plant. In a preferred embodiment, an F1 hybrid corn plant is hybrid corn plant DK580. The present invention further contemplates seed of an F1 hybrid corn plant.
In yet a further aspect, the invention provides an inbred genetic complement of corn plant MBZA. An inbred genetic complement is preferably contained in a seed, a corn plant, or a diploid plant cell. In a preferred embodiment, that inbred genetic complement comprises the RFLP genetic marker profile of Table 5, the genetic isozyme typing profile of Table 6, or both the RFLP genetic marker profile of Table 5 and the genetic isozyme typing profile of Table 6.
In another aspect, the present invention provides a hybrid genetic complement formed by the combination of a haploid genetic complement of corn plant MBZA with a haploid genetic complement of a second corn plant. In a preferred embodiment, the hybrid genetic complement is contained in a seed, corn plant, or diploid plant cell.
In another aspect, the present invention provides a corn plant regenerated from a tissue culture that comprises a hybrid genetic complement of this invention.